HealthDay News — Having excess visceral body fat distribution and biomarkers for insulin resistance are better predictors of an obese individual’s risk for developing type 2 diabetes than general adiposity, study results suggest.

Visceral fat was associated with more than a two-fold increased risk for developing incident diabetes (OR=2.42; 95% CI: 1.59-3.68) among obese participants, James de Lemos, MD, of the University of Texas Southwestern Medical Center in Dallas, Texas, and colleagues reported in the Journal of the American Medical Association. The study is part of the journal’s theme issue on obesity.

Although high BMI is associated with diabetes at a population level, results from previous studies indicate that BMI does not predict diabetes risk within obese populations.

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“Indeed, many obese persons appear resistant to the development of metabolic disease,” the researchers wrote.  “Because the metabolic disease risks associated with obesity are heterogeneous [dissimilar], there remains an unmet clinical need for tools that differentiate obese persons who will ultimately develop prediabetes and diabetes from those who will remain metabolically healthy.”

To identify factors affecting type 2 diabetes risk within this population, de Lemos and colleagues examined body fat distribution, lipid levels and markers of insulin resistance and inflammation in 732 obese adults (BMI of 30 kg/m² or greater), without diabetes or cardiovascular disease who were enrolled in the Dallas Heart Study between 2000 and 2002. Fasting blood glucose was sampled in a subgroup of 512 participants at baseline.

During a median of seven years of follow-up period, the researchers found that 11.5% developed diabetes and 39.1% of individuals with normal baseline glucose levels developed prediabetes or diabetes.

In participants without diabetes at baseline, the following characteristics were associated with higher diabetes risk:

  • Elevated visceral fat: OR 2.42, 95% CI 1.59 to 3.68 (P<0.001)
  • Elevated fructosamine level — OR 1.95, 95% CI 1.43 to 2.67
  • Elevated fasting blood glucose levels — OR 1.88, 95% CI 1.38 to 2.56
  • Family history of diabetes — OR 2.32, 95% CI 1.25 to 4.29 (P=0.008)
  • Elevated Systolic BP — OR 1.26, 95% CI 1.07 to 1.48 (P=0.006
  • Weight gain over follow-up — OR 1.06, 95% CI 1.02 to 1.10 (P=0.002)

The researchers found no associations between BMI, total body fat or abdominal subcutaneous fat and the development of diabetes or prediabetes.

Additionally, among participants with normal fasting blood glucose at baseline, factors significantly associated with incident prediabetes and diabetes were:

  • Higher visceral fat mass — OR 1.48, 95% CI 1.17 to 1.88 (P=0.001)
  • Elevated fructosamine levels — OR 1.42, 95% CI 1.14 to 1.75 (P=0.001)
  • Elevated insulin level — OR 1.34, 95% CI 1.06 to 1.70 (P=0.01)
  • Older age, per 10 years — OR 1.48, 95% CI 1.17 to 1.86 (P=0.001)
  • Non-white race — OR 1.77, 95% CI 1.08 to 2.91 (P=0.02)
  • Family history of diabetes — OR 1.60, 95% CI 1.05 to 2.44 (P=0.03)
  • Weight gain from baseline — OR 1.08, 95% CI 1.05 to 1.10 (P<0.001)

Similarly, there were no associations with general adiposity.

“These findings suggest that clinically measurable markers of adipose tissue distribution and insulin resistance may be useful in prediabetes and diabetes risk discrimination among obese individuals and support the notion of obesity as a heterogeneous disorder with distinct adiposity subphenotypes,” the researchers concluded.

de Lemos JA et al. JAMA 2012; 308:1150-1159.